Method of producing bituminous dispersions



are used as the Patented Sept. 1, 1936 PATENT oFFicE METHOD OF PRODUCINGBITULIINOUS DISPERSIONS Jack Miscall, Rutherford, N. J., assignor, bymesne assignments, to The Patent and Licensing Corporation, New tion ofMassachusetts N Drawing.

York, N. Y., a corpora- Application July 26, 1932,

Serial No. 624,911

8 Claims.

This invention relates to the production of dis persions ofthermoplastic materials, and is particularly concerned with theproduction of soaptype dispersions by means of a colloid mill.

When a colloid mill is in operation, a great amount of air is suckedinto the apparatus by reason of the vacuum created within the mill bythe rapidly rotating parts. The air enters through the packing glands,bearing surfaces, and through loosely connected joints.

In the production of soap-type dispersions of thermoplastic materialsuch as asphalt in an aqueous medium, the presence of air is detrimentalto the success of the operation. The air causes a creaming efiect withthe result that a scum, containing a large proportion of poorlydispersed particles of asphalt, is formed. Additionally, when certainsoaps, such as rosin soap,

emulsifying agent, a chemical reaction occurs between the soap and thecarbon dioxide contained in the air. Rosin is composed chiefly ofabietic acids which are weaker than carbonic acid and thereforedisplaced by the latter. The action of the carbonic acid on the soap isaccelerated at elevated temperatures and hence at the temperature atwhich the emulsion emerges from the colloid mill the reaction proceedsfairly rapidly with the result that rosin is precipitated and the soapdestroyed. As long as the soap is present it acts as a protectivecolloid to maintain the large particles in suspension, but when it isprecipitatedthe particles agglomerate into pellets which form a solidasphalt blanket on the emulsion. In addition, the incorporation of airin the ingredients to be emulsified reduces the friction in the millwith the result that dispersion to the required degree is not effected.Furthermore, the incorporation of air greatly increases the volume ofthe ingredients passing through the milk-sometimes as much as 40%,-- sothat the capacity of the mill is materially reduced and the storagefacilities must be greatly increased to handle the product.

The object of my invention is to provide means whereby to exclude airfrom the colloid mill during the emulsifying process.

Another object of my invention is to provide a method of producingsoap-type emulsions of difficultly emulsifiable asphalts.

In accordance with my invention the colloid mill is immersed in aviscous liquid bath in order to prevent intake of air. A suitable liquidto be used as a bath is a heavy petroleum oil such as fuel oil orcylinder oil, but any other material that has sufiicient viscosity sothat it is not easily sucked into the mill and at the same time is ofsuch nature that it is not injurious to the emulsion when mixedtherewith in small quantities, may be used as the bath.

In practicing my invention the materials to be dispersed are run into acolloid mill of the usual type such as a Hurrell mill and subjected tothe emulsifying action of the mill. The feed to the mill is entirelyclosed and the mill itself is immersed in a receptacle filled withviscous oil or 10 other viscous material, to a sufiicient depth so thatair cannot enter through the packing glands, bearing surfaces or throughjoints which ordinarily allow air to filter through. The dispersion thenpasses from the mill to a receptacle where it may be tested and if foundsuitable, it is pumped to a storage tank, If the emulsion isunsatisfactory it may be recycled through the mill.

I have found that by using an oil bath for the olloid mill it ispossible to satisfactorily emulsify certain types of asphalt which ithas heretofore been difiicult or impossible to emulsify in the millwhich was exposed to the air, or which produced poor emulsions when soemulsifled. Not only has the quality of the dispersion been greatlyimproved but the volume of the emulsion has also been reduced more thanbelow that which is obtained when operating with the mill exposed to theair. 30

To illustrate my invention an emulsion was prepared with a Mexican typeasphalt having the following specifications:

Specific gravity 1.01 to 1.03 Softening point (B. a R.) 102 to 109 F.Penetration (100 gr., 5 sec., 77 F.) 180 to 210 Ductility (77 F.) 100Flash point Over 450 F. Solubility in carbon bisulphide 99.8%

The asphalt was heated to 230F. and proportioned through a colloid millsubmerged in an oil bath, together with a rosin soap solution containing25% excess potassium hydroxide over the amount necessary forsaponification. The soap solution was heated to F. The outlettemperature of the emulsion ranged between F. and F. The resultingemulsion contained 2.5% of soap and 42.5% of water. The emulsion waspassed through a 28 mesh screen and showed 50 a screen deposit of only016%. No scum was formed on the emulsion. An examination of theparticles showed that none greater than 16 mu in size were present,while 70% were 4 mu or less 55 1 due to the character of the asphalt. I

showed 11.8% greater The same asphalt heated to 240 F. was proportionedthrough a colloid mill, which was exposed to the air, together with arosin soap solution containing 22% excess potassium hydroxide. Theemulsion issued from the outlet of the mill at a temperature rangingbetween 170 F;- and 180 The watercontent was-43%and the proportion ofsoap present was 2.2%.. The emulsion contained 25% to 35% of air byvolume, gaveiai very high screen deposit, and formed. 2.2% .ofv scum. Anexamination of" "the particle size than 16 mu and 58% of 4muorless.

The emulsion prepared byusling 'th'e oil immers'ed mill containedabodt"% of air by volume, the source of which is not certain. However,the small amount of air present did-not ma.-,;.. "terially impair thequality of the emulsion.

With other types'of asphalt than effect of aeration is much moreserious." With certain asphalts derived from Mid-Continent or Texasoilsof semi-asphaltic nature,z-.far greater liability to foaming or aerationis encountered. Apparently the surface tension relationship-s of suchasphalts vary .greatly and-a m0repermanentfoam'may result fromaerationin themill With certain asphalts derivedf om such oils andhaving thesame general melting point, pene- 3D.

tration, and ductility characteristics as the Mexican asphalt referr'edto, the'aeration-is; so severe 'that it becomes.practicallyimpossible tomake "a satisfactory emulsion atall in the ordinary inches thick on an;ordinary '55 gallon barrel and 7 completely is aipasty,foamy mixture ofair bubbles, aqueous phase, and agglomerated particles of asphalt, allin a condition which will;not readily-disperse into the better partofthe. emulsion, orifredistributed, re-collects- Thisjfoamy ,materialbreaksdown within; a short time and the emulsion contained in this is,from a practical standinpt'unusabla, Q V

It is difilcult to determine exactly why, under such conditions and withspecific .asphalts of this kind, the effect of aeratiorijshouldfbe soseriously destructive; One reasonable explanatiomho wever, does residein the fact that with .asphalts having low surface tension relationshipto air the foam produced inthe severe action of the mill is quitepermanent. The air bubbles which are .surrounded by theaqueousphasefitwith its the asphalt, is this .kin d, it. will be seenthat any preferential dispersed asphalt) being relatively permanent, mayhave the property of concentrating, on the surface or at the interface,by preferential adsorption, the soap which normally would bedistributable about the asphalt particles. It is well knownthat'inthefinterfa'cial films of dispersions of this kind there is aconcentration of the emulsifying media. Inasmuch as the air, as well asthe dispersed phase in a system of :rladsor-ption of the'emulsifyingagent at the airwater interface would result in diminishing the-stability of the dispersed asphalt while increasing the stability ofthe; foam. The chemical effect 0f; the carbon dioxide in the aeratedemulsion uphereinabove described, doubtless onthe soap, as alsocontributes to the harmful results that en- =sue'when emulsification isaccompanied by aera- Mexican, the

tionand the formation of foam. In running the sameMid CQntinent asphaltas referred to above in 'the mill, in which the feed is closed and inwhich'the glands are" sealed in a bath of oil, this aeration ispracticallyieliminated and the emergent emulsion issub'stantially freefrom foam or scum formation, being of normal particle size and free fromcoarse particles which. produce screen residues, andv is in everyrespectcommercially usable. i f

.I claim as my invention:

1. The process of' emulsifying asphalt which comprises ipassingthemolten asphalt through a colloid millutogether with water and dispersingagent whilesaid colloid mill is immersed in a liquid bath. 3 I a 2..Theprocessof emulsifying asphalt which comprises passing molten asphalttogether with water and..a dispersing agent through a colloid mill andpreventing aeration during the emulsification,.;by thefl actiongofasliquid seal around the bearings of. the mill; -i 3..ln; the process ofproducing 'soap type asphalt emulsions by colloid mill actions the stepwhichjcomprises producing the emulsion in the substantial-absence0f--air by theagency of a liquid-seal, around thebearings-of the colloidmill.

4. The process iof producing soap type asphalt .emulsions'which:comprises passing asphalt in liquidv state {together with water and a.soaplike,..dispersin'gagentthrough a colloid mill while saidm-ill. isimmersedin a. liquid bath.

5.. Process in-accordance with claim 4 in which the bathcomprisespaviscous oil.

6. Inthe production of asphalt emulsions by means of a colloid mill,lthestep .of preventing access of air tosaid mill .byimmersing the mill in aliquid bath. L

'7. -Method according to claim 6 in which the bath is composed of aviscous liquid.

8. Method according to claim 6 in which the liquid .bathis aheavyhydrocarbon oil.

- JACK MISCALL.

